"We were recommended to try a course of injections but unfortunately these have failed to improve his symptoms," Boro boss Gareth Southgate told the club's official website.
"On the advice of specialists, we have therefore decided that the best course of action is for Mido to have a period of rest and rehabilitation.
"Due to the nature of the injury, it is very difficult to put a timescale on it, but what Mido needs to do now is rest from playing football or training with the team.
"The aim of the rehabilitation during this period will be to strengthen the areas around the injury and in particular to work on his core stability.
"Our medical team will work closely with him over the weeks ahead to ensure we eventually have him back fit and raring to go.
"It is frustrating for Mido and for the rest of us to lose him in this way because we all want him out on the pitch and scoring goals.
"But the most important thing is that we resolve the problem, even if, unfortunately, it takes longer than we would like."